A Sunday Post probe can reveal a revamp of Scotland’s busiest rail line is at least £32 million over budget and seven months late because of the wire bungle.

Rail watchdogs have confirmed the delay on the scheme to run electric trains between Glasgow and Edinburgh is due to some of the route’s overhead wires and railway bridge walls being too low to meet vital safety standards.

The blunder, which has meant ripping up and starting again in some sections of the 42-mile link, comes as passengers today face a fresh round of timetable chaos.

Critics last night warned the revelations, which follow a summer of delays on Scotland’s railways, would push passengers’ patience to “the absolute limit” and demanded action from SNP ministers.

But a Sunday Post investigation has laid bare the growing problems with rail improvement projects across the country, including:

An extra £32m was spent on the Edinburgh to Glasgow route last year alone with the overall cost of the £742m scheme set to soar.

Construction on a £175m project to improve the Aberdeen to Inverness rail line was meant to begin in the spring but has no current start date and latest cost estimates are “significantly” over a £191m cap ordered by regulators.

Watchdogs doubt journey time improvements between the central belt and the Highlands will be completed by the target date of 2019.

Labour’s transport spokesman Neil Bibby MSP said: “The travelling public in Scotland have had to endure a summer of delays and disruption. That pattern of disruption is set to continue due to some fundamental errors.

“Meeting safety regulations is a basic requirement of any works being carried out.

“There are serious questions to be asked about how investment in our rail infrastructure is being delivered in this country.

“Just a few weeks ago, the Transport Minister thanked people for their patience but that patience has been pushed to the absolute limit.”

Passengers have been left carrying the cost of the wire height fiasco.

Sales director Lucy Sharp, 38, who uses the service between Edinburgh and Glasgow, said: “This is an utter shambles.

“You wouldn’t mind so much if the fares weren’t sky high. They’re taking us all for utter mugs.”

Transport minister Humza Yousaf admitted in July that electric train services between Edinburgh and Glasgow were unlikely to be completed by December this year – seven months behind schedule.

Mr Yousaf said at the time the news would “increase the cost of the project beyond the previous £742m estimate” but stopped short of giving an updated price tag.

However, the annual financial review of Scotland by the Office Of Rail And Road (ORR) – the independent safety and economic regulator for Britain’s railways – revealed that in 2015/16, a total of £172m was spent on the Edinburgh Glasgow Improvement Programme (EGIP) against a budget of £149m.

“A reassessment of contractor costs and higher than expected
tenders from suppliers” was partly to blame for the higher spend, says the ORR. However, there was also less work carried out than planned because of delays and this equated to £9m in extra costs.

The ORR says this £32m overspend for 2015/16 is likely to be an underestimate. In addition, it says: “The main reason for the higher costs on these projects was a late identification of additional electrification scope required to be compliant with safety legislation.

“In particular, increases to the height of bridge parapets and wire heights through stations relative to the specification Network Rail used, as well as additional screening for line side infrastructure.

“In some cases, this has required both re-design and re-work to completed structures.”

John Finnie MSP, transport spokesman for the Scottish Greens, said: “It’s deeply frustrating that the kind of infrastructure linking cities that other countries take for granted is lagging so far behind here in Scotland.”

A Transport Scotland spokesman said questions about Scotland’s major rail projects would be answered by an ongoing “intensive review of the major rail projects being delivered by Network Rail”.

He added: “Once the review has concluded, the Minister for Transport intends to bring senior Network Rail officials before the Rural Economy and Connectivity Committee to answer questions on delivery and costs, and to address his concerns and those raised by the ORR. “

A Network Rail spokesman said: “We remain committed to delivering our enhancement programme as quickly as possible and are currently reviewing how best to do this as cost-effectively as we can for the taxpayer.”